The Role of Caretaker Turned Dominant

I've been a nurse for nearly two decades now, and I always thought my patients came first. But last week, something changed inside me. My long-term partner and I had talked about experimenting with power dynamics in our relationship, but the idea never really clicked until one night when he was feeling particularly stressed from work. Seeing him like that made me want to take control, to be his protector, his caretaker, not just professionally but intimately too. So, we tried out a light form of dominance and submission play, with me in charge for the first time. I felt both scared and exhilarated; it was unlike anything else in my life. But why did this sudden shift happen? How can someone who cares so much about others suddenly crave power over their partner? Am I crossing a line here, or is there something healthy and necessary to explore in our relationship dynamic? What do you think? Have any of you experienced a similar change in your own relationships?